JP2015161290A - catalyst temperature estimation device - Google Patents

Abstract

The estimation accuracy of a catalyst temperature at the time of fuel cut is improved by executing correction of the estimated temperature when fuel cut is started in one cylinder.
In a catalyst temperature estimating device (43) provided with a temperature estimating means (44) for estimating the temperature of a catalyst provided in an exhaust passage (33) of a multi-cylinder engine (1), fuel cut is started in at least one cylinder of the multi-cylinder engine (1). A fuel cut determination means 45 is provided, and the temperature estimation means 44 corrects the estimated temperature when the fuel cut determination means 45 determines that the fuel cut has started.
[Selection] Figure 1

Description

  The present invention relates to a catalyst temperature estimation device, and more particularly to a catalyst temperature estimation device that improves the estimation accuracy of a catalyst temperature when a fuel cut is performed.

  In the engine, the temperature of the exhaust purification catalyst provided in the exhaust passage is estimated, and the fuel injection amount is controlled so that the catalyst does not become overheated. For example, in JP2013-7375A, the temperature of the catalyst provided in the exhaust passage is estimated, the fuel injection amount is controlled based on the estimated temperature, the wall flow rate of the fuel injection port is estimated, and the wall flow rate is calculated. Accordingly, there has been disclosed a technique for improving the estimated temperature accordingly to improve the estimation accuracy of the catalyst temperature, and for preventing the catalyst from overheating by prohibiting the fuel cut and increasing the fuel. (Patent Document 1).

JP 2013-7375 A

By the way, in the fuel cut of the multi-cylinder engine, as shown in FIG. 4, when the fuel cut condition is satisfied by the accelerator OFF (accelerator pedal return), the fuel cut is performed for all the cylinders.
Immediately after the fuel cut, the fuel adhering to the port wall surface that has been formed up to that point flows into the catalyst together with the air in an unburned state, and the afterburning of the catalyst is promoted. Therefore, immediately after the fuel cut, correction is performed to add a constant rising temperature to the estimated catalyst temperature.
In a multi-cylinder engine, when fuel cut is started even for one cylinder, the fuel adhering to the wall surface of the port communicating with the one cylinder becomes lean and flows into the combustion chamber and is sent to the catalyst without being burned. The possibility is great, and in that case, oxygen in the intake fresh air is also sent to the catalyst as it is, so that the oxidation reaction is promoted by the catalyst. In the fuel cut to a cylinder (for example, one cylinder) that is less than all cylinders, such as a minute accelerator opening degree or a shift change, the post-catalyst burning phenomenon occurs as described above, so the catalyst temperature rises.

However, in the conventional control of Patent Document 1, if all the cylinders are not fuel cut, correction for adding a constant temperature increase to the estimated catalyst temperature is not calculated, and the estimated catalyst temperature does not increase. Therefore, when fuel cut is performed on cylinders that are less than all cylinders, as shown in FIG. 4, the estimated catalyst temperature (solid line) and the actual catalyst temperature (broken line) deviate.
Therefore, in Patent Document 1, since the high temperature of the catalyst is not simulated, there is a problem that the catalyst temperature rises without increasing the amount of fuel for protecting the exhaust system, leading to a decrease in catalyst function due to the high temperature of the catalyst.

  Therefore, the present invention has been made in view of the above problems, and by correcting the estimated temperature when fuel cut is started with one cylinder, the accuracy of estimation of the catalyst temperature at the time of fuel cut is improved. The purpose is to improve.

  The present invention relates to a catalyst temperature estimation device including temperature estimation means for estimating a temperature of a catalyst provided in an exhaust passage of a multi-cylinder engine, and determines that fuel cut is started in at least one cylinder of the multi-cylinder engine. And a fuel cut determining means for correcting the estimated temperature when the fuel cut determining means determines that the fuel cut has started.

  The present invention can improve the estimation accuracy of the catalyst temperature at the time of the fuel cut by executing the correction of the estimated temperature when the fuel cut is started with one cylinder. As a result, the present invention suppresses the difference between the estimated catalyst temperature and the actual catalyst temperature and can simulate the high temperature of the catalyst, so that it is possible to increase the amount of fuel for protecting the exhaust system and to suppress the increase in the catalyst temperature. Thus, the catalyst function can be prevented from lowering.

FIG. 1 is a system configuration diagram of the catalyst temperature estimation apparatus. (Example) FIG. 2 is a control flowchart of the catalyst temperature estimating apparatus. (Example) FIG. 3 is a timing chart showing the relationship between the estimated catalyst temperature and the actual catalyst temperature during fuel cut. (Example) FIG. 4 is a timing chart showing the relationship between the estimated catalyst temperature and the actual catalyst temperature during fuel cut. (Conventional example)

  Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the present invention. In FIG. 1, the multi-cylinder engine 1 includes four cylinders 2 to 5, and includes intake ports 6 to 9 and exhaust ports 10 to 13 communicating with the respective cylinders 2 to 5.
The multi-cylinder engine 1 includes an intake passage 18 that sequentially connects an air cleaner 14, an intake pipe 15, a throttle body 16, and an intake manifold 17 as an intake system, and through which intake air supplied to the cylinders 2 to 5 flows. The throttle body 16 is provided with a throttle valve 19. The intake manifold 17 includes a surge tank 20 and intake branch pipes 21 to 24 that supply intake air to the four cylinders 2 to 5, respectively. The intake branch pipes 21 to 24 are provided with fuel injection valves 25 to 28 for injecting fuel for each of the intake ports 6 to 9.
Further, the multi-cylinder engine 1 has an exhaust manifold 29, a front exhaust pipe 30, a catalyst 31, and a rear exhaust pipe 32 sequentially connected as an exhaust system so that exhaust gas discharged from each cylinder 2-5 flows. A passage 33 is provided. The exhaust manifold 29 has exhaust branch pipes 34 to 37 through which exhaust gases discharged from the four cylinders 2 to 5 flow, respectively.
The fuel injection valves 25 to 28 are connected to the engine control device 38. In the engine control device 38, as means for inputting control information, an intake air amount sensor 39 for detecting the intake air amount flowing through the intake passage 18, a throttle sensor 40 for detecting the throttle opening of the throttle valve 19 as an accelerator operation amount, A crank angle sensor 41 for detecting the crankshaft rotation angle for calculating the engine rotation speed and an oxygen sensor 42 for detecting the oxygen concentration in the exhaust gas flowing through the exhaust passage 33 upstream of the catalyst 31 are connected. Yes.
The engine control device 38 controls the injection amount of each fuel injection valve 25-28 so as to generate the driver's requested driving force based on information input from each sensor 39-42, and the fuel cut condition is When it is established, the fuel injection valves 25 to 28 are controlled to stop the injection.

The multi-cylinder engine 1 includes a catalyst temperature estimation device 43 that estimates the temperature of the catalyst 31 provided in the exhaust passage 33. In this embodiment, the catalyst temperature estimating device 43 is installed in the engine control device 38. The engine control device 38 uses the temperature of the catalyst 31 estimated by the catalyst temperature estimation device 43 to control the injection amount of each fuel injection valve 25 to 28 so that the catalyst 31 is not overheated.
The catalyst temperature estimation device 43 includes a temperature estimation unit 44 that estimates the temperature of the catalyst 31 and a fuel cut determination that determines that a fuel cut has been started in at least one of the four cylinders 2 to 5 of the multi-cylinder engine 1. Means 45 are provided.
The temperature estimating means 44 obtains the load of the multi-cylinder engine 1 from the intake air amount detected by the intake air amount sensor 39 and the engine rotational speed detected by the crank angle sensor 41, for example, and estimates the temperature of the catalyst 31 from the engine load. For example, the fuel cut determination unit 45 satisfies the fuel cut condition in which the accelerator operation amount detected by the throttle sensor 40 is OFF and the engine rotation speed detected by the crank angle sensor 41 is equal to or greater than a predetermined value, and the fuel injection valves 25-28. When the fuel injection is controlled to stop, it is determined that the fuel cut has started.
The temperature estimation unit 44 corrects the estimated temperature when the fuel cut determination unit 45 determines that the fuel cut starts.
Further, the catalyst temperature estimating device 43 corrects the estimated temperature in accordance with the fuel cut cylinder number detecting means 46 for detecting the number of cylinders in which the fuel cut has been performed in the multi-cylinder engine 1 and the number of cylinders in which the fuel cut has been performed. And a calculation means 47 for calculating the quantity. The calculating means 47 increases the correction amount of the estimated temperature as the number of cylinders in which the fuel cut has been performed increases.

Next, as shown in FIG. 2, the catalyst temperature estimation device 43 of the multi-cylinder engine 1 that explains the operation, when the control program starts (101), determines whether the fuel cut condition is satisfied by the fuel cut determination means 45. Judgment is made (102).
If the fuel cut condition is not satisfied and the determination (102) is NO, the correction amount = 0 is calculated by the calculation means 47 (103), the estimated temperature is corrected with the calculated correction amount = 0, and the program ends. (104). When the fuel cut condition is satisfied (FIG. 3: t0) and the determination (102) is YES, the fuel cut is performed by the engine control device 38 (105), and the fuel cut is performed by the fuel cut cylinder number detecting means 46. It is determined that the number of cylinders n is 1 (106).
When the number of cylinders n is 1 and the determination (106) is YES, the correction means = A1 (A1> 0) is calculated by the calculation means 47 (107), and the estimated temperature is corrected with the calculated correction amount = A1 (FIG. 3: Perform t1) to end the program (104). If the number of cylinders n is not 1 and the determination (106) is NO, it is determined that the number n of cylinders that have performed fuel cut is 2 (108).
When the number of cylinders n is 2 and the determination (108) is YES, the calculation means 47 calculates the correction amount = A2 (A2> A1) (109), and corrects the estimated temperature with the calculated correction amount = A2 (FIG. 3: Perform t2) to end the program (104). If the number of cylinders n is not 2 and the determination (108) is NO, it is determined that the number n of cylinders that have performed fuel cut is 3 (110).
If the number of cylinders n is 3 and the determination (110) is YES, the calculation means 47 calculates the correction amount = A3 (A3> A2) (111), and corrects the estimated temperature with the calculated correction amount = A3 (FIG. 3: Perform t3) to end the program (104). If the number of cylinders n is not 3 and the determination (110) is NO, the number n of cylinders that have performed fuel cut is set to 4 (112), and the calculation means 47 calculates the correction amount = A4 (A4> A3) ( 113) The estimated temperature is corrected with the calculated correction amount = A4 (FIG. 3: t4), and the program is ended (104).

Thus, the catalyst temperature estimation device 43 can improve the estimation accuracy of the catalyst temperature at the time of fuel cut by executing the correction of the estimated temperature when the fuel cut is started in one cylinder.
Accordingly, as shown in FIG. 3, the catalyst temperature estimation device 43 can simulate the high temperature of the catalyst 31 while suppressing the deviation between the estimated catalyst temperature (solid line) and the actual catalyst temperature (broken line). Thus, it is possible to increase the amount of fuel for protecting the exhaust system, and it is possible to prevent the catalyst function from being lowered by suppressing an increase in the catalyst temperature.
Further, the catalyst temperature estimation device 43 detects the number of cylinders in which the fuel cut has been performed in the multi-cylinder engine 1, and calculates the correction amount of the estimated temperature in accordance with the number of cylinders in which the fuel cut has been performed. Since the correction amount of the estimated temperature can be set finely, the difference between the estimated catalyst temperature and the actual catalyst temperature can be reduced.
Further, the catalyst temperature estimation device 43 increases the estimated temperature correction amount as the number of cylinders in which the fuel cut is performed is increased, so that the estimated temperature is corrected to be higher as the number of cylinders in which the fuel cut is performed is increased. Therefore, the estimation accuracy of the catalyst temperature at the time of fuel cut can be improved.

  The present invention can improve the estimation accuracy of the catalyst temperature at the time of fuel cut, suppress the increase in the catalyst temperature and prevent the catalyst function from being lowered, and a multi-cylinder engine having a catalyst in the exhaust passage It can be applied to fuel control.

DESCRIPTION OF SYMBOLS 1 Multi-cylinder engine 2-5 cylinder 18 Intake passage 31 Catalyst 33 Exhaust passage 38 Engine control apparatus 39 Intake amount sensor 40 Throttle sensor 41 Crank angle sensor 42 Oxygen sensor 43 Catalyst temperature estimation apparatus 44 Temperature estimation means 45 Fuel cut determination means 46 Fuel Cut cylinder number detection means 47 Calculation means

Claims (3)

  In a catalyst temperature estimation device comprising temperature estimation means for estimating the temperature of a catalyst provided in an exhaust passage of a multi-cylinder engine, fuel cut determination for determining that fuel cut has been started in at least one cylinder of the multi-cylinder engine And a temperature estimation unit that corrects the estimated temperature when the fuel cut determination unit determines that the fuel cut is started.   Fuel cut cylinder number detection means for detecting the number of cylinders in which the fuel cut has been performed in the multi-cylinder engine, and calculation means for calculating a correction amount of the estimated temperature according to the number of cylinders in which the fuel cut has been performed The catalyst temperature estimation apparatus according to claim 1, wherein:   The catalyst temperature estimation apparatus according to claim 2, wherein the calculation means increases the correction amount of the estimated temperature as the number of cylinders in which the fuel cut is performed increases.

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